Farmers utilize multiple vehicle types for tending farm land, whether the work includes preparing the soil or planting or harvesting the crops. Vehicles include tractors for pulling hitched implements (e.g., plows, discs, combines, shredders, balers, etc.) and field application vehicles, or farm vehicles (e.g., row crop sprayers) for spraying fertilizers, pesticides and insecticides.
Row crop sprayers have certain features that are important for minimizing crop damage when spraying. For example, the clearance under the machine is important to provide crop clearance to allow spraying of chemicals with minimal crop disturbance through the growing cycle of the crop. In addition, the total drive package width at the wheel is also important to allow the wheel and drive package to move through certain row spacing with minimal crop damage. In this regard, the sprayer must be able to have adjustable wheel spacing to accommodate different row spacing of crops in various areas of the world.
Some current mechanical drive sprayers utilize a conventional axle (i.e., a straight axle with no drop). With this design, increased crop clearance was obtained simply by increasing the size of the tire and wheel used. This design offers limited crop clearance and wheel track adjustment is not easily accomplished. In other examples, a gear drop box is added to increase crop clearance, but the width of the drive package is increased due to this gearbox.
Farms may vary significantly in size. They range from single household operations to larger commercial or corporate operations that own or lease large tracts of land. While the types of vehicles utilized for these farms are similar in function, they differ in size. For example, tractor horsepower ratings may vary from 44 horsepower for small farm tractors up to 570 horsepower and greater for tractors used for larger operations.
Likewise, field application vehicles also range in size generally in accordance with the capacity of the vehicle. The types of vehicles differ, however, the suspension of the vehicle is an important component for nearly all of them. The suspension is important because it provides comfort for the driver over rough terrain and also enables constant or consistent application of the particular substance being applied to the land or crop. For example, the suspension will absorb at least some of the impact energy as the vehicle traverses rough terrain (e.g., terraced land, creek beds, or washouts due to flooding and erosion). It is important that the impact energy is not substantially transferred to the application equipment, which may result in interruption of the application, over application in a given area, or overspray of the application.
One problem with designing suspension systems capable of handling rough terrain while applying potentially hazardous chemicals is the cost associated with the capacity to haul a large volume of substance for application. For example, increased field application vehicle capacity requires more than merely adding a larger bulk tank to hold a substance for application. A larger tank may result in more weight for the vehicle requiring a stronger motor, more robust driveline components, and a stouter, more sophisticated suspension.
In addition, there are field operation requirements which must be satisfied. For example, typical applicator vehicles (i.e., sprayers) operate by tracking between the crop rows. Applicator vehicles must also maintain a minimum height in order to clear the crop and thus avoid damaging or destroying the crop during the application of a particular substance. Small farm vehicles having light duty drive and suspension systems are adequate for small application needs, however, such designs would not be efficient for larger operations. Larger operations require larger vehicles to carry heavier loads yet maintain the minimum height to prevent crop damage.
In this manner, the relationship between the desired capacity and the operational environment (e.g., the size of the farm) must be considered in the design of the particular vehicle. For larger farms, the increased costs associated with a larger capacity application vehicle may be substantial. For example, in order to provide large field application vehicles capable of safely carrying the weight of a loaded bulk container (e.g., substance capacity ranging from 800-1200 gallons) one design utilizes hydrostatic drive trains. Such systems are complicated and more costly than standard drive shaft systems or chain drive systems, but are best suitable for large capacity systems and can provide maneuverability without damaging crops. For these systems, standard suspensions incorporating leaf springs may be used.
For smaller field application vehicles having 300-400 gallon capacity, chain drive systems may be used. Typically, these vehicles use narrow tires for driving in between the crop rows and carry application equipment that may expand over 3 to 4 rows. Suspension systems for these vehicles may be nonexistent or simply provided by deflating the vehicle tires to soften the ride.
The need arises, however, for a field application (or farm) vehicle which has a capacity for mid-size farms (i.e., a capacity between that for a small application vehicle and that for a large application vehicle) yet the farm vehicle must incorporate a drive system and suspension system which can operate safely within the operational environment utilizing components which fit within the economics of such farms. For example, existing farm vehicles fail to safely meet this need partly because the ground clearance of conventional farm vehicles is dependent on wheel diameter. Increasing wheel diameter to increase ground clearance would raise the farm vehicle's center of gravity to an unsafe height, making it especially prone to rollover on rough terrain.
Thus there is a need for a vehicle which can operate within a farm environment without damaging crops having a drive and suspension system capable of carrying a large quantity of field application material.